acosmin

Try opening functions.php, find these lines:

if ( $is_enabled ) {
    $class = ' mini-disabled';
}

Change to:

if ( $is_enabled || is_single() || is_page() ) {
    $class = ' mini-disabled';
}

Beyond what I said above also do this, open sidebar-browse.php and find:

<?php if ( !get_theme_mod( 'ac_disable_minisidebar' ) ) { // Disable or Enable Mini-Sidebar ?>

Change it to:

<?php if ( !get_theme_mod( 'ac_disable_minisidebar' ) || !is_single() ) { // Disable or Enable Mini-Sidebar ?>

You can try this, open sidebar-browse.php, find:

<?php if ( !get_theme_mod( 'ac_disable_minisidebar' ) ) { // Disable or Enable Mini-Sidebar ?>

Change it with:

<?php if ( !get_theme_mod( 'ac_disable_minisidebar' ) || !is_single() ) { // Disable or Enable Mini-Sidebar ?>

Also open single.php, find:

<section class="container<?php ac_mini_disabled() ?> clearfix">

Change it with:

<section class="container mini-disabled clearfix">

I haven’t tried it, so I don’t know if it really works.

Please read the documentation, Menus section.

To remove the browse more button open header.php and delete the following lines:

<?php if ( !get_theme_mod( 'ac_disable_minisidebar' ) ) { ?>
        <a href="#" class="browse-more" id="browse-more"><?php echo ac_icon('caret-down', false) . __( 'Browse', 'acosmin' ) ?></a>
        <?php } ?>

Can you post some links to your websites?

The Ad code should be something like:

<a href="link"><img src="img link" /></a>

Make the logo smaller…

And serach for .logo-image and remove max-width: 180px;

I am sorry but it’s not possible.

Both your requirements are big customization work. I can only help you with support for bugs and questions regarding theme options.

You can open functions.php and find these lines:

set_post_thumbnail_size( 600, 400, true );
add_image_size( 'ac-post-thumbnail', 600, 400, true );

Change with:

set_post_thumbnail_size( 600, 400 );
add_image_size( 'ac-post-thumbnail', 600 );

After that you might want to use this plugin Regenerate Thumbnails.